ParticipantsChrista Wille, Madison, WI (Presenter) Nothing to Disclose
Samuel A. Hurley, PhD , Madison, WI (Abstract Co-Author) Nothing to Disclose
Nagesh Adluru, PhD, Madison, WI (Abstract Co-Author) Nothing to Disclose
Rebecca Alcock, Madison, WI (Abstract Co-Author) Nothing to Disclose
Bryan C. Heiderscheit, PhD, Madison, WI (Abstract Co-Author) Research Consultant, Altec, Inc;
Richard Kijowski, MD, Verona, WI (Abstract Co-Author) Research support, General Electric Company; Consultant, Boston Imaging Core Lab, LLC
wille@ortho.wisc.edu
PURPOSEThe purpose of this investigation was to quantify changes in muscle microstructure following acute hamstring strain injury (HSI).
METHOD AND MATERIALSCollegiate athletes with an HSI (n=16) underwent a magnetic resonance image (MRI) exam of the bilateral thighs using a GE MR750 3.0T scanner and 32-channel torso coil at a mean of 4 (± 2.5) days following injury. MRI exam included coronal and axial fat-suppressed T2-weighted fat/water IDEAL scan (44 cm FOV, 256x256, 44 slices, 4 mm thk, 5 mm gap; TR/TE 7418/86.8 ms) to identify regions of edema and axial DTI sequences. Diffusion weighted images were acquired with b=500 s/mm2, 30 directions, 6 b=0 volumes (48 cm FOV, 160x160, 72 slices, 3 mm thk; TR/TE 5770/51.1 ms), and repeated with reversed phase-encode direction. Distortion, eddy current, and motion correction were performed using FSL TOPUP and EDDY (FMRIB Software Library). Axial parameter maps of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and principal effective diffusivity eigenvalues (λ1, λ2, λ3) were created. Deterministic streamline tractography was performed using Euler integration with a step size of 0.1 mm (stopping criteria: 45° curvature and 0.20 FA thresholds). Mean DTI-parameters were identified for regions of injury within contractile muscle tissue using manual segmentation and compared to identical regions on the uninvolved limb with a Mann-Whitney-U test.
RESULTSDTI-parameters demonstrate a significant decrease in FA (p=0.046) and significant increase in MD (p=0.025), RD (p<0.01), λ2 (p=0.021), and λ3 (p<0.01) in the region of injury compared to the mirrored region of normal muscle. Tractography from a selected subject demonstrates the effects of reduced FA on the involved limb (right) with fewer continuous fiber tracts present within the region of injury (purple) compared to the mirrored region of normal muscle on the uninvolved limb.
CONCLUSIONSignificant muscle microstructural changes are detectable using DTI in athletes following an HSI. Decreased FA and increased diffusivity in regions of injured muscle indicate less restricted water diffusion, likely due to disruption of muscle fibers following injury.
CLINICAL RELEVANCE/APPLICATIONDTI-parameters can quantify microstructural changes in injured muscle and may have potential in guiding effective treatment following HSI.